package leetcode;

public class RomanToInteger {

	public int romanToInt(String s) {  
	        int ret = toNumber(s.charAt(0));  
	        for (int i = 1; i < s.length(); i++) {  
	            if (toNumber(s.charAt(i - 1)) < toNumber(s.charAt(i))) {  
	                ret += toNumber(s.charAt(i)) - 2 * toNumber(s.charAt(i - 1));  
	            } else {  
	                ret += toNumber(s.charAt(i));  
	            }  
	        }  
	        return ret;  
	    }  
	      
	    public int toNumber(char ch) {  
	        switch (ch) {  
	            case 'I': return 1;  
	            case 'V': return 5;  
	            case 'X': return 10;  
	            case 'L': return 50;  
	            case 'C': return 100;  
	            case 'D': return 500;  
	            case 'M': return 1000;  
	        }  
	        return 0;  
	    }  
}
